In recent years peptide hormones and regulators of bodily functions have been discovered, e.g., bradykinin, enkephalin, TRH and LH-RH. In addition, other peptides having valuable properties have been discovered, e.g., aspartame.
In an effort to improve the activity and properties of these peptides, particularly the propensity to enzyme cleavage, extensive research has been conducted. One of the approaches taken has been to attempt to introduce a dehydro amino acid into the peptide sequence without adversely affecting the biological properties and optical activity of the compounds. Since most amino acids and peptides are optically active and only one stereoisomer has the desired biological properties, a sought after means to produce dehydropeptides is one that does not racemize the compound. This has been difficult to accomplish since processes which result in dehydro amino acids and dehydropeptides usually are conducted under conditions which result in an undesirable extent of racemization.
There is thus a need for a facile synthesis of optically active dehydropeptides having desirable biological properties and stability to enzyme cleavege.